Apparatus and method for combating crops with a heated air flow

Abstract

An apparatus and a method for combating crops with a heated air flow involve a gas burner unit that is only activated if the pressure, the flow rate or the rotational speed of the ventilator is greater than a determined threshold value; and the gas burner unit is again deactivated if the pressure, the flow rate or the rotational speed of the ventilator is less than the determined threshold value.

The invention claimed is: 
     
       1. An apparatus for combating crops with heated air comprising:
 a ventilator configured to generate an air flow; 
 a gas burner unit configured to heat the air flow generated by the ventilator; 
 an outflow channel configured to receive the air flow heated by the gas burner unit and guide it through the outflow channel to an outflow opening where the crops to be combatted are exposed to the heated air flow; 
 a controller operatively connected to the gas burner unit, wherein: 
 the apparatus further comprises a sensor operatively connected to the controller which is arranged in the air flow and is configured to monitor a pressure and/or a flow rate of the air flow generated by the ventilator; and in that: 
 the controller is configured to: 
 only activate the gas burner unit if the pressure or the flow rate of the air flow generated by the ventilator is more than a determined threshold value; and 
 deactivate the gas burner unit again if the pressure and/or the flow rate of the air flow generated by the ventilator is less than the determined threshold value. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the apparatus further comprises a sensor operatively connected to the controller configured to monitor a rotational speed of the ventilator;
 and in that 
 the controller is further configured to: 
 only activate the gas burner unit if the rotational speed of the ventilator is greater than a determined rotational speed threshold value; and 
 deactivate the gas burner unit again if the rotational speed of the ventilator is less than the determined rotational speed threshold value. 
 
     
     
       3. The apparatus according to  claim 1 , wherein the apparatus further comprises an operating element coupled to the controller which is configured to:
 activate and deactivate the ventilator; and/or 
 control a rotational speed of the ventilator, and 
 wherein the controller is further configured to control the gas burner unit in response to signals from the sensor for the pressure and/or the flow rate of the generated air flow and/or the sensor for the rotational speed of the ventilator. 
 
     
     
       4. The apparatus according to  claim 2 , wherein the controller is further configured, to run the ventilator at a determined idle rotational speed that is lower than the determined rotational speed threshold value, at least for a determined period of time after deactivation of the gas burner unit. 
     
     
       5. The apparatus according to  claim 1 , wherein the apparatus further comprises at least one flame detector coupled to the controller which is positioned in a combustion chamber of the gas burner of the gas burner unit at a determined distance from a fuel input:
 wherein the determined distance is sufficiently large, so that a flame, of which a flame front is not reaching beyond a determined distance upstream of the outflow opening, is detected; and 
 wherein the determined distance is sufficiently small, so that a flame, of which the flame front is reaching beyond the determined distance upstream of the outflow opening is not detected, since the distance from the fuel input to a base of the flame is greater than the determined distance, and 
 wherein the controller is configured to deactivate the gas burner unit if the at least one flame detector is not detecting a flame. 
 
     
     
       6. The apparatus according to  claim 5 , wherein the at least one flame detector comprises an ionization sensor. 
     
     
       7. An assembly for use in an apparatus according to  claim 1 , wherein:
 the assembly comprises the gas burner unit and the outflow channel coupled thereto; 
 the assembly forms a one-part portable unit and further comprises a handle configured to allow an operator to hold the assembly by hand and to carry it by hand during operation; 
 wherein length of the gas burner of the burner unit according to a flow direction of the air flow is in the range of 5-25 cm; and 
 wherein length of the outflow channel according to the flow direction of the air flow is in the range of 50 cm-200 cm. 
 
     
     
       8. A method for controlling an apparatus according to  claim 1  wherein the sensor monitors a pressure and/or a flow rate of the air flow generated by the ventilator, the method comprising:
 using the controller, only activating the gas burner unit if the pressure or the flow rate of the air flow generated by the ventilator is greater than the determined threshold value; and 
 using the controller, deactivating the gas burner unit again if the pressure and/or the flow rate of the air flow generated by the ventilator is less than the determined threshold value. 
 
     
     
       9. The method according to  claim 8 , wherein the controller:
 only activates the gas burner unit if a rotational speed of the ventilator is greater than a predetermined threshold value; and 
 deactivates the gas burner unit again if the rotational speed of the ventilator is less than the predetermined threshold value. 
 
     
     
       10. The method according to  claim 8 , wherein the controller controls the gas burner unit in function of the sensor for the pressure and/or the flow rate of the generated air flow and/or the sensor for a rotational speed of the ventilator. 
     
     
       11. The method according to  claim 8 , wherein the controller causes the ventilator run at a determined idle rotational speed that is less than the determined threshold value, at least for a determined period of time after deactivation of the gas burner unit. 
     
     
       12. The method according to  claim 8 , wherein the controller deactivates the gas burner unit if a flame detector is not detecting a flame, and
 wherein the flame detector is positioned in a combustion chamber of the gas burner of the gas burner unit at a certain distance from fuel input: 
 wherein a determined distance is sufficiently large, so that a flame, of which a flame front is not reaching beyond a determined distance upstream of the outflow opening, is detected; and 
 wherein the determined distance is sufficiently small so that a flame, of which the flame front is reaching beyond the determined distance upstream of the outflow opening is not detected, since the distance from the fuel input to a base of the flame is larger than the determined distance. 
 
     
     
       13. The method according to  claim 12 , wherein the flame detector comprises an ionization sensor. 
     
     
       14. A method for manufacturing the apparatus according to  claim 1 , the method comprising:
 coupling the gas burner unit and the outflow channel to provide an assembly; and 
 manufacturing the assembly as a one-part portable unit comprising a handle configured to allow an operator to hold the assembly by hand and carry it by hand during operation; 
 wherein length of the gas burner of the gas burner unit according to a flow direction of the air flow is in the range of 5-25 cm; and 
 wherein length of the outflow channel according to the outflow direction of the air flow is in the range of 50 cm-200 cm.